Federer's failure, on the heels of a shock second-round Wimbledon exit, thwarted a potential quarter-final match with 12-time grand slam winner Rafael Nadal, who had a four-set win over German 22nd seed, Philipp Kohlschreiber.

"The way I played," Federer said, "I couldn't have beaten Rafa."

Instead, it will be Robredo, in his first US Open quarter-final, awaiting the winner of a later match between Nadal, who is 6-0 against his countryman, and Germany's 22nd-seeded Philipp Kohlschreiber.

Robredo, who had lost his 10 prior matches against the Swiss star, suffered seven prior fourth-round US Open defeats and matched his best grand slam performance by finally breaking through.

"I'm delighted. Today the difference is I won the break points and he did not," said 31-year-old Robredo.

"It was a really, really tough night and I am so happy. It was really a great experience."

Federer won only two of 16 break-point chances.

"That was not a very good close," Federer said.

"It just ended up being a bad combination of many things."

Federer hit 45 winners but also made 43 unforced errors and managed only five aces while Robredo hit 70 per cent of his first serves and won four of his seven break chances.

In taking as many sets off Federer as he had in their 10 prior matches combined, Robredo also raised questions about the future of the 32-year-old former world number one, who had not missed the US Open quarter-finals since a fourth-round exit in 2003.

"I'm going to feel like I beat myself," Federer said. "It was up to me to make the difference and I just couldn't. I self destructed, which is really disappointing. When things came to the crunch I just couldn't do it. It's frustrating."

Federer had made 36 consecutive Grand Slam quarter-final appearances before being upset by Ukrainian Sergiy Stakhovsky in the second round at Wimbledon, having not departed a major before the last eight since the 2004 French Open.

It was the first time Federer has missed the last-eight in consecutive slams since the 2003 Australian and French Opens, just before he won his first major crown at Wimbledon later that same year.

Federer, whose seventh seeding at the US Open was his lowest at a grand slam event since 2002, failed to match the career record of 41 Slam quarter-finals by retired US star Jimmy Connors.

Rain delay forces court change

A rain delay of more than four hours pushed Federer's match from Arthur Ashe Stadium to Louis Armstrong Stadium, marking the first time since a 2006 triumph over Frenchman Marc Gicquel that Federer had played at the secondary court.

Federer's only defeat in eight prior Armstrong appearances came when he lost to Spain's Juan Carlos Ferrero in the third round in 2000 in US first US Open.

"Amazing, eh," Robredo said. "I beat the best guy of all times in a great stadium like this where he loves to play."

Federer had made eight career comebacks to win after dropping the first two sets but he failed on five break points in the fourth game of the third set, which Robredo held to reach 2-2, and there was a sense a comeback chance had been squandered.

Robredo broke Federer at love in the seventh game for a 4-3 edge and they held to set up Robredo serving for the match in the 10th game, fans chanting, "Let's Go Roger" in vain hopes of willing the wilting once-king to a rally for the ages, only to watch as Robredo held again to win in two hours and 24 minutes.

Robredo took advantage of his fourth break point in the opening game of the match but handed Federer a break to 2-2 when he swatted a forehand beyond the baseline.

Federer netted a volley to hand Robredo a 5-4 lead but the Spaniard could not claim the set on his serve, Federer equalizing when Robredo swatted a forehand long on the way to a tie-breaker.

Robredo won the final four points to take the first set, the last of them on a 120-mph ace, and seized command by breaking Federer at love in the eighth game of the second set for a 5-3 edge.

Nadal recovers to beat Kohlschreiber

World number two Rafael Nadal avoided the same fate which befell Roger Federer to reach the quarter-finals with a 6-7 (4/7), 6-4, 6-3, 6-1 win over Kohlschreiber.

Nadal, the 2010 champion in New York, stayed on course for a 13th Grand Slam title and will next face fellow Spaniard Robredo.

Second seed Nadal fired 48 winners and took his year record to 57 wins against just three defeats and his perfect hardcourt form to 19 wins.

He also preserved his record this year at the tournament of not having dropped serve, although he had a rocky start to the evening against the big-hitting Kohlschreiber, who finished with 49 winners but 47 unforced errors.

Nadal certainly had the 29-year-old German under the cosh throughout their last-16 tie, carving out 21 break points, converting five.

"It was very tough tonight with the humid conditions, I was sweating too much," said Nadal after three hours and 12 minutes on court.

"I had chances in the first set but couldn't take them. I feel lucky to be through as it was physically tough.

"But as the match went on I felt more comfortable on my serve."

Next up for Nadal is Robredo against whom he has a 6-0 record.

"He's playing great and he has had similar circumstances like me in coming back from injury," said Nadal.

Ferrer will next face French eighth seed Richard Gasquet after he outlasted Canadian 10th seed Milos Raonic 6-7 (4/7), 7-6 (7/4), 2-6, 7-6 (11/9), 7-5 after four hours and 40 minutes and despite the Canadian's 39 aces, the third-most ever in a US Open match.

Ferrer is 8-1 all-time against Gasquet, whose only prior fourth-round slam win in 17 attempts came on his way to a 2007 Wimbledon semi-final.